Alex,

This makes a lot of sense. If there are new images that are edited 
versions of source images I'd probably create a relationship between 
the new and source objects, using a predicate like "isVersionOf" or 
"isDerivedFrom". Or if it's the *aggregation* of the 3 images that's 
new, and the source images themselves are used as is, I'd create the 
new object with "hasMember" relations to the 3 source images. That's 
how we handle e.g. postcards: the front and back views are each a 
separate object, and there's a logical "postcard" object above them 
with bilateral hasMember/isMemberOf relationships connecting them. 
One of our CModels for that logical object is, in fact, 
CModelCompositeObject.

If you have a logical object that has 3 images that are edited 
versions of source images, the relationships might look something 
like this (the bidirectional links are, of course, optional):

TopObject -> hasMember  -> NewImage1
TopObject -> hasMember  -> NewImage2
TopObject -> hasMember  -> NewImage3

NewImage1 -> isDerivedFrom -> Image1
NewImage2 -> isDerivedFrom -> Image2
NewImage3 -> isDerivedFrom -> Image3

If you were creating an application that lets someone identify a 
repository image and grab a copy to edit and save, that application 
would manage the link form the new to the old object. And the source 
object wouldn't have to be updated; the new image canjust  point back 
to it.

At 11:03 AM +0100 9/10/10, Alex Rodriguez Lopez wrote:
>Hi Peter and Patrick,
>
>Thank you both for this input, I've been actualy truggling with this
>collections / aggregations issue too for some time, but as we haven't
>started to develop our repo system yet (just at the design phase) I
>didn't know how Fedora could manage this (if it could).
>
>The methodology and conclusions both of you reached will be valuable for
>our case!
>
>But I was wondering, here we have one more use case, regarding
>relationships between objects too, let me explain:
>
>Apart from this 2 types of collections both of you suggested:
>
>- Permanent/curated collection (system created or externaly aggregated)
>
>- Ad-hoc/custom collection (user created)
>
>The user should have the option of creating *new* objects, based on
>other objects (being on a collection or not), so they are creating a
>*composite* object, not a collection, which would efectively have to be
>considered a new object, but still maintain the relation to the used
>objects in it. So the user can, for example, grab 3 images from the
>local repo or other sources, edit them and add some other stuff
>(effectively creating a new object) and save them for their (and
>everybody's) use, but retaining this info about the relations (so it is
>known that other images are integrated inside). I would call this a
>*composite object*, as opposed to that 2 types of *collections of objects*.
>
>Does this make sense? Has any one in the list had to apply this in a
>Fedora repo?
>
>TIA
>
>Regards,
>
>Alex
>

-- 
_______________________________
Peter C. Gorman
Head, University of Wisconsin Digital Collections Center
218 Memorial Library
Madison, WI 53706
[email protected]
(608) 265-5291


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